Rotary evaporators are in widespread use in virtually every laboratory in the world, for removing solvents from organic and inorganic solutions, to yield a liquid or solid product.
The evaporators work by placing a sample in a round-bottom flask, typically a pear-shaped flask, which spins on an axis at an angle while sitting in a water bath. The flask is attached to a motor, which includes a rotary joint that enables the flask to spin, while permitting the evaporated solvent to flow through the joint (vapor duct) and come into contact with one or more condensers. The condenser(s) cool the vapor, and the resulting cooled vapor (i.e., liquid) then flows down to a flask below the condenser, where it can be collected.
A water bath is typically provided to supply sufficient heat to the flask to evaporate the solvent. Typically, the rotor, the motor, the rotary joint, the condenser, the flask used to hold the original solvent, and the flask used to hold the condensed vapor as it is collected, are all connected while the unit is in operation. A mechanical arm is usually provided to raise and lower the connected parts, to bring the flask out of the water bath, although this can also be accomplished using a motorized means.
The condenser of the rotary evaporator can be connected to a water source, and water is frequently acceptable to condense the solvent of interest, particularly if the solvent has a relatively high boiling point. Users frequently leave the water flowing through the condenser throughout the day, which results in large volumes of waste water. Further, where the solvent has a particularly low boiling point, it can be advantageous to cool the vapor to temperatures cooler than a water condenser can provide. To only use a water-cooled condenser might create an environmental issue, as a significant volume of volatile organic solvent would not be collected, and enter into the environment.
Particularly when low boiling solvents are used, efforts have been made to improve on the condensation of the vapors so as to trap a significant portion of the solvents. In such cases, one approach is to use a dry-ice condenser, which is packed with dry ice, and, optionally, a solvent that forms a slurry with dry ice to maintain a given temperature (for example, dry ice-acetone maintains a temperature of −78° C.). This can be a burden to the scientists, who have to replace the dry ice in their condensers throughout the day, particularly where a laboratory has a significant number of scientists accessing the same source of dry ice.
Other efforts to lower the temperature of the condenser beyond that provided by running water have included using chillers. Chillers are attached to the condenser using the entrance and exit ports on the water-cooled condensers through which water would otherwise flow, and the cooling liquid is continuously recycled through the chillers. One limitation of the chillers is that the fluids tend to be only marginally cooler than water (i.e., they are typically limited to fluids that are cooled to around −15 to −20° C.). Another limitation is that they can be extremely expensive.
It would be advantageous to provide additional rotary evaporators that provide integrated cooling in a manner in which low boiling solvents are efficiently trapped. The present invention provides such rotary evaporators.